This application claims benefit of Japanese Application No. Hei11-368192 filed in Japan on Dec. 24, 1999, the contents of which are incorporated by this reference.
1. Field of the invention
The present invention relates to a structure of a zoom lens barrel having a moving frame (frame member) to be advanced or retracted through a cam follower.
2. Related Art Statement
In recent years, compact cameras have been reduced in size and employ a high-magnification zoom function and other novel functions. Corresponding to these trends, various types of moving frame retracting mechanisms of a lens barrel have been proposed.
For example, a lens barrel disclosed in Japanese Patent Application Laid-Open No. HEI7-191249 has plural lens holding frames capable of being advanced or retracted and a cam frame for advancing or retracting the lens holding frames. The cam frame has three cam grooves wherein three cam followers provided on the lens holding frame are fit slidably coupled thereto. By driving the cam frame, the cam followers are driven along the cam grooves so as to advance or retract the plural lens holding frame. The three cam grooves are formed such that a part of a cam curve line of a cam groove intersects an introduction groove for introducing the cam follower. Therefore, compactness of the cam frame is achieved.
However, according to the lens barrel disclosed in the aforementioned Japanese Patent Application Laid-Open No. HEI7-191249, when a cam follower is located at a intersecting position between the cam follower introducing groove and the cam groove, there is a possibility that a smooth motion of the cam follower may be hampered. Further, the cam curve lines have to be formed by shifting their phase so that when a cam follower is located at an intersecting position, the other two cam followers are never located at intersecting positions of the cam grooves. Thus, there is a restriction about the configuration of the cam frame.
The present invention has been achieved to solve the above-described problems and an object of the invention is to provide a zoom lens barrel having a cam follower and cam grooves for advancing or retracting a lens holding frame for holding a lens directly or indirectly, and another object of the invention is to provide a lens barrel system incorporating the zoom lens barrel ensuring an excellent space efficiency and achieving reduction of the size and compactness.
The zoom lens barrel of the present invention has a first lens holding frame capable of moving in the direction of the lens optical axis and having a first cam follower, a second lens holding frame capable of moving in the direction of the lens optical axis and having a second cam follower and a cam ring having first and second cams which maintain a sliding contact with the first and second cam followers so as to control movement of the first and second lens holding frames in the direction of the optical axis. An end portion of the second cam includes an opening portion at a cam ring end face in which the first and second cam followers are introduced. An end of the first cam is joined to the other end of the second cam as if the first cam is returned from the other end of the second cam. The first cam and second cam are formed to extend side by side. When the cam ring is rotated, the first and second cam followers are driven by the first and second cams in the direction of the lens optical axis, so that the first and second lens holding frames are moved in the direction of the lens optical axis.
The other features and benefits of the present invention will be apparent from the following description.